With the arrival of a ubiquitous information society, a terminal is demanded to transfer information anytime, anywhere. For such a terminal, flexible, light-weight, and inexpensive electronic devices are required, but the previous devices using inorganic materials such as silicon does not sufficiently meet the requirement. Accordingly, in recent years, electronic devices using organic materials as semiconductors or the like are intensively studied for satisfying such requirements. As a p-type organic semiconductor, there are known materials such as pentacene capable of forming a thin film through a dry process and P3HT (poly(3-hexylthiophene)) capable of forming a thin film through a wet process.
Beside, as n-type organic semiconductors, there are known materials such as fullerene capable of forming a thin film through a dry process and PCBM ([6,6]-phenyl-C61-methyl butyrate) capable of forming in a thin film through a wet process. However, these materials are not satisfactory from the viewpoint of stability in atmosphere, because it is necessary to seal them in order to prevent them from deterioration in atmosphere when they work as electronic devices. Further, there is known hexadecafluoro copper phthalocyanine (F16 Cu Pc) that has characteristics of reduced deterioration in atmosphere. However, there is a problem that because of low solubility to solvent, this compound is not suitable for forming a thin film through a wet process (“Yuki Toranjista no Dosasei Kojogijutsu [Zairyo Kaihatsu Sakuseiho Sosi Sekkei] (Technology of improving operation properties of Organic transistors [Development of materials, Production methods, Design of elements]” under supervision of Kazuhiro kudo, Gijutsu Johokyokai (2003) p 48 to 49, and Chemistry of Materials 16, 4436 to 4451 (2004)).
In view of the above, it is required to develop n-type organic semiconductor materials that have characteristics of reduced deterioration in atmosphere and that are suitable for forming a thin film according to a wet process (e.g., a liquid coating process).
Organic semiconductors are useful as photoelectric conversion materials for producing organic photoelectric conversion devices such as organic thin film solar cells. These devices are easier to be manufactured than those of an inorganic semiconductor such as silicon and the like. In particular, organic semiconductors capable of forming a film through a wet process have potential to realize devices having a large area, at low temperature, and at low cost. So far, for example, an organic thin film solar cell using a mixed film of P3HT and PCBM as a photoelectric conversion layer is reported, but its photoelectric conversion performance is inferior to that of silicon devices. Consequently, further improvements in the performance are required. One of the reasons for a low energy conversion efficiency of an organic thin film solar cell is a narrow wavelength region in which materials of the cell can absorb and photo-electrically convert, taking the wavelength range of the sun light into consideration. In particular, the organic thin film solar cell can not effectively utilize a light in a long wavelength region (“Yukihakumaku Taiyodenchi no Saishingijutsu (Latest Technology for Organic Thin Film Solar Cell)”, supervised by Kaku Uehara, Susumu Yoshikawa, CMC Inc. (2005) pp. 1-8, and MRS Bulletin, 30, 33-36 (2005)).
Accordingly, it is required to develop organic semiconductor materials which are suitable for film formation through a wet film forming process (e.g., a liquid coating process), and exhibit light absorption and photoelectric conversion properties even in a long wavelength region.